View source for Help:Fancy diagram

The Diagram from $\rm The\ \TeX{}Book$, p. 182:

$$
\def\normalbaselines{\baselineskip20pt\lineskip1pt\lineskiplimit0pt }
\def\noalign{}
\def\vskip#1pt{}
\def\hidewidth{}
\def\mapright#1{\smash{
    \mathop{\longrightarrow}\limits^{#1}}}
\def\mapdown#1{\Big\downarrow
  \rlap{\vcenter{\hbox{$\scriptstyle#1$}}}}
\matrix{\noalign{\vskip6pt}&&&&&&0\cr
  &&&&&&\mapdown{}\cr
  0&\mapright{}&{\cal O}_C&\mapright\iota&
    \cal E&\mapright\rho&\cal L&\mapright{}&0\cr
  &&\Big\Vert&&\mapdown\phi&&\mapdown\psi\cr
  0&\mapright{}&{\cal O}_C&\mapright{}&
    \pi_*{\cal O}_D&\mapright\delta&
    R^1f_*{\cal O}_V(-D)&\mapright{}&0\cr
  &&&&&&\mapdown{\theta_i\otimes\gamma^{-1}}\cr
  &&&&&&\hidewidth R^1f_*\bigl({\cal O}
    _V(-iM)\bigr)\otimes\gamma^{-1}\hidewidth\cr
  &&&&&&\mapdown{}\cr
  &&&&&&0\cr\noalign{\vskip6pt}}
$$

Here is the $\rm \TeX$ code, as used in Knuth's book, to show the mathjax compatibility with plain $\rm \TeX$. 

(For a $\rm \LaTeX$- encoding see [[Talk:EoM:This_project#Commutative_diagrams_in_TeX.2FLaTeX | here]].)

<nowiki>
<pre>
\def\normalbaselines{\baselineskip20pt\lineskip1pt\lineskiplimit0pt }
\def\noalign{}
\def\vskip#1pt{}
\def\hidewidth{}
\def\mapright#1{\smash{
    \mathop{\longrightarrow}\limits^{#1}}}
\def\mapdown#1{\Big\downarrow
  \rlap{\vcenter{\hbox{$\$$\scriptstyle$\#1\$$}}}}
\matrix{\noalign{\vskip6pt}&&&&&&0\cr
  &&&&&&\mapdown{}\cr
  0&\mapright{}&{\cal O}_C&\mapright\iota&
    \cal E&\mapright\rho&\cal L&\mapright{}&0\cr
  &&\Big\Vert&&\mapdown\phi&&\mapdown\psi\cr
  0&\mapright{}&{\cal O}_C&\mapright{}&
    \pi_*{\cal O}_D&\mapright\delta&
    R^1f_*{\cal O}_V(-D)&\mapright{}&0\cr
  &&&&&&\mapdown{\theta_i\otimes\gamma^{-1}}\cr
  &&&&&&\hidewidth R^1f_*\bigl({\cal O}
    _V(-iM)\bigr)\otimes\gamma^{-1}\hidewidth\cr
  &&&&&&\mapdown{}\cr
  &&&&&&0\cr\noalign{\vskip6pt}}
</pre>
</nowiki>